There is a liquid phase lifting method in which a seed crystal, which is a base of crystal growth, is immersed in molten silicon while being rotated and is then gradually lifted, on producing an ingot of Si. However, since SiC does not have liquid phase below 3000° C., therefore a sublimation recrystallization method is widely adopted. However, a manufacturing technique of the SiC wafers is not matured, and many of wafers that can be manufactured contain crystal defects in crystal. Since crystal of good quality is not obtained in large-diameter wafers, the size of α-SiC single crystal wafer for SiC semiconductors and GaN emission laser, which is made available for practical use, is limited to about two inches, though it is sold on the market.
On the other hand, as for a device, which can handle an ordinary silicon single crystal wafer, there exist the ones which handle the wafers of 6 inches to 12 inches, and no semiconductor manufacturing line can handle α-SiC single crystal wafers of the size of two inches, which are smaller than the above wafers. This makes it possible to manufacture SiC wafers in the size of two inches available for practical use, but they cannot be provided to the actual industrial world. There is an increased demand especially for putting α-SiC single crystal wafers into practical use, because the α-SiC single crystal wafer has high dielectric strength. Consequently, it is desired to handle this in the semiconductor manufacturing line.
As the above-described manufacturing method of large-diameter silicon single crystal wafers, Japanese Patent Laid-open No. 10-55975 is known. This manufacturing method is for growing polycrystal or single crystal Si around an Si single crystal rod. However, since the silicon single crystal rod is used for a raw material, the device becomes large-scaled, and the raw material applied to this method is only Si, but SiC that is a promising semiconductor material is not disclosed. Further, the obtained double ring layer structure Si is about 1.1 times as large as the raw material diameter and it is difficult to call it achievement of a large diameter.
Paying attention to the above-described problem of the prior art, from the viewpoint of economically manufacturing the SiC semiconductor devices, the present invention has its object to provide a large-diameter SiC wafer, which utilizes the present Si device manufacturing line to make it possible to handle the SiC wafers, and the manufacturing method thereof.